Comparative analysis of bisphenol-A removal efficiency from water: equilibrium, kinetics, thermodynamics and optimization evaluations

This work examined the comparative sorption efficiency of Bisphenol-A (BPA) from water using four adsorbents: commercial activated carbon (AC), magnetic commercial activated carbon (MAC), activated carbon from walnut shell (AW) and magnetic activated carbon from walnut shell (MAW), respectively. The structural composition of AC, MAC, AW and MAW was studied by X-ray diffraction (XRD) spectroscopy and Fourier transform infrared (FT-IR). Batch sorption studies at different physicochemical properties under different experimental conditions were carried out. Data generated were subjected to kinetic, isotherm models and optimized using Box-Behnken design. Results showed that BPA uptake increases as the pH becomes more acidic and peaked at 2. Kinetic results indicated pseudo-first-order kinetics thus signifying physical adsorption mechanism. Langmuir isotherm gave a better fit compared to Freundlich isotherm, with maximum adsorption capacity of 55.48, 61.67, 89.23, and 92.27 mg/g for AW, AC, MAW, and MAC, respectively. Also, the thermodynamics data demonstrated that the process of adsorption was spontaneous, feasible and endothermic. Furthermore, regression equations of the experimental data derived using linear, quadratic, factorial design and cubic interaction models showed that the regression coefficient of quadratic model was much closer and congruent compared to the rest of the model. Thus, the magnetic adsorbents can be considered to be better adsorbents when compared with the non-magnetic forms. [GRAPHICS] .